auth: factor code responsible for the NSEC{,3} QType bitmap computation

[miodvallat]

Short description

There are two large blocks of code computing NSEC and NSEC3 record type bitmap values, with subtle differences between them.

This PR factors the two large common parts, which makes the distinction between NSEC and NSEC3 processing more visible.

There are absolutely no functional changes intended. However I forgot to switch the Kärcher™ off and got side-tracked with minor extra changes:

• removal of dead code in DNSPacket
• since an early version of that PR horribly broke the *-*-both tests because of missing domain_id field assignments and confused the record signing code, I have added, for records which are synthesized, either explicit assigment of that field when the proper value is known, or an annotation that the value remains the default value.

Checklist

I have:

• read the CONTRIBUTING.md document
• read and accepted the Developer Certificate of Origin document, including the AI Policy, and added a "Signed-off-by" to my commits
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)

[coveralls]

Coverage Report for CI Build 26738384166

Coverage decreased (-5.5%) to 66.542%

Details

• Coverage decreased (-5.5%) from the base build.
• Patch coverage: No coverable lines changed in this PR.
• 7483 coverage regressions across 95 files.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

7483 previously-covered lines in 95 files lost coverage.

Top 10 Files by Coverage Loss	Lines Losing Coverage	Coverage
pdns/recursordist/pdns_recursor.cc	1096	29.25%
pdns/recursordist/lua-recursor4.cc	681	0.0%
pdns/recursordist/rec-main.cc	522	45.06%
pdns/recursordist/rec-tcp.cc	450	20.67%
pdns/recursordist/rec_channel_rec.cc	391	15.49%
pdns/recursordist/lwres.cc	353	24.13%
pdns/recursordist/rec-lua-conf.cc	347	2.49%
pdns/recursordist/syncres.cc	343	72.38%
pdns/recursordist/rec-rust-lib/cxxsupport.cc	341	48.68%
pdns/recursordist/rpzloader.cc	291	29.88%

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Coverage Stats

Relevant Lines:	132747
Covered Lines:	97901
Line Coverage:	73.75%
Relevant Branches:	64198
Covered Branches:	33151
Branch Coverage:	51.64%
Branches in Coverage %:	Yes
Coverage Strength:	3373123.3 hits per line

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💛 - Coveralls